Generalization and Instantiation
While discussing aggregation and exhibition, we talked about entire groups of objects or processes—any scientific paper, any employee, any running. However, what if we wanted to consider the example of a specific paper, written by a certain John Doe? Or if we wanted to consider a group of employees, namely managers, who receive a certain salary out of the range of salaries available for the company? Perhaps we would like to discuss running in a marathon, as opposed to just any kind of running? We need to be able to pay particular attention to a specialized group, which belongs to a more general group, or even a specific instance out of a class of objects. As its name clearly points out, generalization-specialization is the relation between a general and a special case of a thing. Classification-instantiation is the relation between a class of things and a unique instance from the class. Since these two concepts are important to systems modeling, we consider them two of the four fundamental relations; and since they are intimately related, they are discussed and explained together in this chapter.
KeywordsStructural Relation Object Class Process Instance Object Instance Process Class
- Coad, R. and Yourdon, E. Object-Oriented Analysis. Prentice-Hall, Englewood Cliffs, NJ, 1991.Google Scholar